Kerry Sieh TO Annual Meeting 13 November 2007

1. Behavior of the Sunda Megathrust in Sumatra Kerry Sieh TO Annual Meeting 13 November 2007 Soft corals lifted about 10 cm during the September 2007 earthquakes

2. Collaborators Caltech John Galetzka Mohamed Chlieh Don Helmberger JP Avouac Aron Meltzner Ozgun Konca Yaru Hsu Mark Simons Andrew Kositsky Indonesian Institute of Sciences Danny Natawidjaja Bambang Suwargadi Dudi Prayudi Imam Suprihanto Scripps Yehuda Bock Paul Jameson Peng Fang Linette Prawirodirjo Kyoto University Shigehiro Fujino USC Jose Borrero • Sponsors Soft corals lifted about 10 cm during the September 2007 earthquakes

3. To understand the behavior of a great active fault at time scales important to understanding the earthquake cycle. Through the millennia Through the centuries During large earthquakes

4. from Rich Briggs, after Briggs et al 2006 Deformation over millennia base modified from NASA World Wind/Blue Marble

6. Deformation over centuries southern Aceh-Andaman section Nias-Simeulue section Mentawai section The earthquake cycle by Rich Briggs

7. Nias-Simeulue and southern Aceh-Andaman sections Fossil Microatoll deaths in ~1440 Fossil Microatoll deaths in ~1390 Fossil Microatoll deaths in ~1327 Fossil Microatoll deaths in 1861 Fossil Microatoll deaths in 1843 Fossil Microatoll deaths in ~1799 (tentative) from Aron Meltzner

8. The Mentawais

9. 1797 & 1833 AD 1357±14 2007 Sawtooth curve of paleoseismic events Not yet published Elevation relative to modern sea level Years (AD) Bulasat

10. 2007 Sawtooth curve of paleoseismic events Not yet published Elevation relative to modern sea level 0.15 m ~0.2 m? 1.5±0.3 m 1.4±0.2 m 1.8±0.1 m Years (AD) Simanganya

12. Narrow trench-parallel graben on an islet west of South Pagai island

14. Victims of uplift -- dead Portuguese Men-o-War Southern tip of South Pagai island

15. Measurements Vertical deformation in the field from Briggs et al (2006) Mega island, 4˚S

16. Minor emergence near northern end of uplift Island at the western entrance to Sikakap strait

17. Field measurements

19. Map of field measurements Not yet published

20. Map of contoured field measurements Not yet published

21. Map of contoured field measurements Not yet published

22. Map of contoured field measurements Not yet published

23. L-band InSAR from the Japanese ALOR satellite

24. cGPS measurements Sumatran GPS Array (SuGAr) as of Sept 13, 2007 proposed early 2008

25. from Ozgun Konca

26. Displacements during the Mw8.4 mainshock Map of cGPS displacements Not yet published Horizontal (black) and vertical (red) from Peng Fang via Ozgun Konca

27. Mw 8.4 Silabu (SLBU) 15-sec data Not yet published 15-sec K2 data Not yet published 1-sec data Not yet published Strong-ground-motion from Chris Stephens via Ken Hudnut cGPS from Jeff Genrich

28. Comparison of K2 and cGPS velocity records at Silabu

29. Displacements during the Mw7.9 aftershock Map of SuGAR vectors Not yet published Horizontal (black) and vertical (red) from Peng Fang via Anthony Sladen

30. Mw 7.9 and 7.0 aftershocks Silabu (SLBU) 10 cm 15-sec data Not yet published 15-sec K2 data Not yet published 7.0 7.9 1-sec data Not yet published 1-sec 10 cm 7.9 10 min Strong-ground-motion from Chris Stephens via Ken Hudnut cGPS from Jeff Genrich

31. Pukarayat (PKRT) 15-sec data Not yet published 7.9 15-sec 1-sec data Not yet published Mw 7.9 and 7.0 aftershocks 7.9 7.0 cGPSfrom Jeff Genrich

32. Displacements during the Mw7.0 aftershock Map of SuGAR vectors Not yet published Horizontal (black) and vertical (red) from Peng Fang via Anthony Sladen

33. Mw8.4 inversions Analyses Maps of inversions Not yet published Teleseismic data only cGPS and teleseismic data Data = black Model horizontal (red) and vertical (gray) by Ozgun Konca

34. Mw8.4 inversions Detail Map of inversions Not yet published cGPS with coral at Mega Data = black Model horizontal (red) and vertical (gray) by Ozgun Konca

35. Mw8.4 inversions Model displacements Vertical (m) Maps of vertical deformation estimated from inversion of SuGAR data Not yet published Horizontal from cGPS data only by Ozgun Konca

36. Joint seismic/cGPS inversion of the 7.9 aftershock Maps of inversion Not yet published Data = black Model horizontal = red and vertical = gray by Anthony Sladen

37. Joint seismic/cGPS inversion of the 7.9 aftershock Maps of inversion Not yet published by Anthony Sladen

38. Tsunami field data Measurements of runup along mainland coast Not yet published by Jose Borrero

39. Combined source of mainshock and two aftershocks -- Mw8.45 Maps of slip from inversion Not yet published Data = black Model horizontal = red Model vertical = gray by Anthony Sladen

40. Calculated interferogram from combined model from Jean-Philippe and Anthony

41. How do the Sept 2007 events fit in to the long-term picture? Map Not yet published Comparison of 50-year coupling and September events Base map from Mohamed Chlieh

42. from Mohamed, Anthony and Jean-Philippe

43. Map comparing slip in 2007 with slip deficit since 1833 and 1797 Not yet published Accumulated potential slip versus slip during 8.4 in September

44. 1797 1833 Natawidjaja et al, JGR, 2006

45. Maps of 2007 uplift Not yet published 1833 2007

46. 1797 & 1833 2007 Sawtooth curve of paleoseismic events Not yet published Elevation relative to modern sea level Years (AD) Bulasat

47. by Rich Briggs